Foxy headset confusion - please help!

my 2011 foxy has an FSA No 57 headset, tapered head tube with a straight 1 1/8 steerer. I want to put in a tapered fork, but am confused about which new headset I need.

As far as I can see, the current crown race is what enables the steerer to be straight and fit the tube. Is it a case of simply a new crown race for a tapered steerer, or do I need a new headset? If so, I'm unsure of what to get in terms of sizes etc.